Numerous drugs, medications and other substances are inhaled into the lungs for rapid absorption in the blood stream and systemic delivery, or alternatively for therapeutic treatment locally. Inhaled drugs are typically either in aerosolized or powder form. In either case, the delivered agent should have a particle or droplet nuclei size that is 5 microns or less in order to reach the terminal ramifications of the respiratory tree.
Such small particles are, however, thermodynamically unstable due to their high surface area to volume ratio, which provides significant excess surface free energy and encourages particles to agglomerate. Agglomeration of the particles and adherence of the particles to the internal surfaces of the inhaler result in delivery of particles too large in size, delivery of a lower dose, due to particle adherence to the interior surfaces of the inhaler, poor flow and non-uniform dispersion, which results in the delivery of a varying dosage. In addition, as noted above, many dry powder formulations employ larger excipient particles to promote flow properties of the drug. However, separation of the drug from the excipient, as well as the presence of agglomeration, can require additional inspiratory effort, which, again, can impact the stable dispersion of the powder within the air stream of the patient. Unstable dispersions may inhibit the drug from reaching its preferred deposit/destination site and can prematurely deposit undue amounts of the drug elsewhere.
Further, the hygroscopic nature of many dry powder drugs may also require that the device be cleansed (and dried) at periodic intervals.
Therefore, there remains a need for a dry-powder inhalation device that facilitates the dispersion of active drug powder and delivers a consistent dose to the deep lung and is not plagued by the above-described limitations.